This application claims priority of European Patent Application No. 01 303 023.4, filed Mar. 29, 2001. This invention relates to a tension control apparatus and tensioning method for an aero-mechanical conveyor. Aero-mechanical conveyors are often used to convey powders and other particulate matter by entraining the particulate matter in a moving airstream. Such conveyors typically include an endless wire rope assembly upon which dividers are fastened and used for carrying particulate matter. The rope assembly is typically carried on drive and driven pulleys enclosed within infeed, corner and discharge semi-circular housings in various configurations. The housings are interconnected by two tubes through which the rope assembly travels as it moves around the drive and driven pulleys. As the conveyor operates, forces are exerted on the rope assembly that can cause the rope assembly to stretch. Such forces are created by normal wear on the conveyor, the weight of the material being conveyed along the rope assembly, and similar other factors, and can cause the rope assembly to stretch to the point that the amount of tension initially exerted on the rope assembly is inadequate.
While prior art manual tension adjusting mechanisms exist for moving the head and tail pulley assemblies relative to each other to maintain the correct amount of tension on the rope assembly, such mechanisms are often inadequate. For example, some traditional prior art tension adjusting mechanisms rely on clamps which fasten the semi-circular housings to the tubes. Tension on the rope assembly is adjusted by loosening the bolts that hold the clamps in place and sliding one or both of the housings inwardly or outwardly relative to the tubes. Another prior art method of adjusting the tension on the rope assembly involves moving the drive or driven pulley together with the housing. Regardless of which prior art method is employed, adjusting the tension by moving the housings relative to the conveyor tubes is a manual operation. In addition, the discharge end of the equipment is frequently inaccessible, making access to the tube-joining clamps challenging. The clamps nonetheless have to be slackened and re-tightened. Furthermore, once the tension has been adjusted, there is no guarantee that the tubes and the connecting spigots leading to the housings will be properly aligned, which makes jamming almost inevitable.
The invention of the present application overcomes the problems inherent to the prior art described above by providing a tension control apparatus for use on an aero-mechanical conveyor that adjusts tension by moving the housings and pulley assemblies automatically and without requiring any significant manual intervention. The tension control apparatus of the present invention uses compression springs to maintain a pre-selected amount of tension on the rope assembly. One embodiment of the invention also uses cams to ensure that the drive centers cannot be pulled together by an increase in tension on the rope assembly due to the exertion of drive or other forces. The present invention can accommodate a total rope stretch of 16 mm before the tension control apparatus must be reset, and includes a novel reset lever which provides a visual indication of when such a reset is needed. The invention of the present application not only provides a simple procedure for accurately resetting the tension on the rope assembly, but also permits a user to quickly and easily reset the tension to an amount equivalent to that originally set at commissioning, thereby ensuring that an adequate amount of tension is maintained on the rope assembly at all times.
Therefore, it is an object of the present invention to provide an aero-mechanical conveyor having components which facilitate easy handling and installation, and provide low maintenance operation.
It is another object of the present invention to provide an aero mechanical conveyor that includes a tension control apparatus that provides a visual and repeatable indication of the tensioning force applied to the rope assembly on the conveyor.
It is another object of the present invention to provide an aero-mechanical conveyor that includes sliding seals having a negligible, constant frictional drag, thereby permitting the force being applied to the rope assembly by the tensioning arrangement to be easily determined.
It is another object of the invention to provide an aero mechanical conveyor that includes a tension control apparatus capable of continuous use 365 days each year.
It is another object of the present invention to provide an aero-mechanical conveyor that includes a tension control apparatus which can be used in vertical, angled or horizontal aero-mechanical conveyor systems.
These and other objects of the present invention are achieved in the preferred embodiments disclosed below by providing an improved tension control apparatus for use in an aero-mechanical conveyor for moving bulk materials. The conveyor includes upper and lower housings, and head and tail pulley assemblies mounted on respective shafts positioned within the upper and lower housings, respectively. Spaced-apart inflow and outflow conveyor tubes interconnect the upper and lower housings. An endless rope assembly is disposed within the conveyor tubes and around the head and tail pulley assemblies. The improvement includes a bracket that cooperates with the inflow and outflow conveyor tubes. A guide sleeve is carried by the bracket for receiving a push rod. The push rod extends along the length of the conveyor tubes from the guide sleeve to the upper housing and includes an upper end engaging the head pulley assembly and a lower end extending through the guide sleeve. A tensioning assembly engages the lower end of the push rod and is carried by the bracket for urging the push rod against the head pulley assembly, thereby urging the head pulley assembly away from the tail pulley assembly and maintaining the rope assembly in a tensioned condition.
According to one preferred embodiment of the invention, the bracket is carried on the inflow and outflow conveyor tubes.
According to another preferred embodiment of the invention, the tensioning assembly includes a spring carried thereon urging the tensioning assembly against the push rod for maintaining the rope assembly in the tensioned condition.
According to yet another preferred embodiment of the invention, the tensioning assembly further includes at least one upper plate connected to the bracket and guide sleeve. A lower plate engages the lower end of the push rod. At least one bolt interconnects the upper and lower plates and includes a first end extending through the lower plate; and a second end extending through the upper plate. The second end has a complementary nut releasably attached thereto for being selectively tightened or loosened for urging the upper and lower plates toward or away from each other, thereby respectively increasing or decreasing the tensioned condition of the rope.
According to yet another preferred embodiment of the invention, the spring is concentrically positioned along the length of the bolt and captured between the upper plate and the nut, thereby permitting the spring to contract or expand in response to a respective increase or decrease in the tensioned condition of the rope.
According to yet another preferred embodiment of the invention, the tensioning apparatus includes a cam carried on the push rod. The cam is in abutting engagement with a cam follower carried on the push rod and is positioned for rotation against the cam follower caused by upward movement of the cam follower in response to a decrease in the tensioned condition of the rope assembly, thereby maintaining the rope assembly in a preselected tensioned condition.
According to yet another preferred embodiment of the invention, the improvement further includes first and second dust cap seals interconnecting the inflow and outflow conveyor tubes with the upper housing for reducing emissions of particulate matter from the conveyor.
According to yet another preferred embodiment of the invention, one of the first and second dust cap seals is positioned on a respective one of the inflow and outflow conveyor tubes for permitting sliding, sealing movement of the inflow and outflow conveyor tubes relative to the upper housing, thereby correcting radial misalignment of the tubes relative to the upper housing and reducing friction on the rope assembly.
A method for maintaining a predetermined tension on an endless rope assembly of an aero-mechanical conveyor is provided in which the rope assembly is disposed around head and tail pulleys mounted on respective shafts positioned within upper and lower housings and positioned within spaced-apart inflow and outflow conveyor tubes interconnecting the upper and lower housings. The method include the steps of providing a bracket cooperating with the inflow and outflow conveyor tubes, and providing a guide sleeve carried by the bracket for receiving a push rod. The push rod extends along the length of the conveyor tubes from the guide. sleeve to the upper housing and includes an upper end engaging the head pulley assembly and a lower end extending through the guide sleeve. The method also includes the step of providing a tensioning assembly which engages the lower end of the push rod. The tensioning assembly is carried by the bracket for urging the push rod against the head pulley assembly, thereby moving the head pulley assembly away from the tail pulley assembly and maintaining the rope assembly in the tensioned condition. The head and tail pulley assemblies are positioned at a preselected fixed center distance relative to one another, thereby placing the rope assembly in the predetermined tensioned condition. The tensioning assembly is adjusted within a range of adjustment to compensate for a decrease in the tensioned condition of the rope assembly, thereby adjusting the center distance and the tensioned condition as the tension control apparatus operates.
A method for maintaining a predetermined tension on an endless rope assembly of an aero-mechanical conveyor according to yet another preferred embodiment of the invention is provided in which the tensioning apparatus includes a cam carried on the push rod and in abutting engagement with a cam follower carried on the push rod. The cam is positioned for rotation against the cam follower caused by upward movement of the cam follower in response to a decrease in the tensioned condition of the rope assembly, thereby maintaining the rope assembly in a preselected tensioned condition.